Dorzolamide hydrochloride, chemically (4S,6S)-4-(ethylamino)-5,6-dihydro-6-methyl-4H-thieno[2,3-b]thiopyran-2-sulfonamide 7,7-dioxide hydrochloride, which has the formula (1):
is a carbonic anhydrase inhibitor. Dorzolamide hydrochloride ophthalamic solution is indicated in the treatment of elevated intraocular pressure in patients with ocular hypertension.
Analytical profiles of drug substnaces and excipients, volume 26, p-283–317 mentioned two crystalline forms of dorzolamide hydrochloride (form I, II).
It has now been found that dorzolamide hydrochloride can be prepared in a novel crystalline form (form III). The novel crystalline form is stable and is not spontaneously converted to the previously known forms. The novel form is found to be suitable for pharmaceutical preparations.
The object of the present invention is to provide a stable novel crystalline form of dorzolamide hydrochloride, a process for preparing it and a pharmaceutical composition containing it.